/**
 * Copyright 2009 the original author or authors.
 *
 * Licensed under the GPL License, Version 3.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.gnu.org/licenses/lgpl-3.0.txt
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.guardianapis.api.util;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * This utility class was clone from an equivalent class at http://www.w3.org/International/URLUTF8Encoder.java
 * 
 * @author michael.lee
 *
 */
public class URLEncoder {

	/*******************************************************************************
	 * Constants
	 *******************************************************************************/

	private static Log log = LogFactory.getLog(URLEncoder.class);
	
	final static String[] hexCharacters = {
		"%00", "%01", "%02", "%03", "%04", "%05", "%06", "%07",
		"%08", "%09", "%0a", "%0b", "%0c", "%0d", "%0e", "%0f",
		"%10", "%11", "%12", "%13", "%14", "%15", "%16", "%17",
		"%18", "%19", "%1a", "%1b", "%1c", "%1d", "%1e", "%1f",
		"%20", "%21", "%22", "%23", "%24", "%25", "%26", "%27",
		"%28", "%29", "%2a", "%2b", "%2c", "%2d", "%2e", "%2f",
		"%30", "%31", "%32", "%33", "%34", "%35", "%36", "%37",
		"%38", "%39", "%3a", "%3b", "%3c", "%3d", "%3e", "%3f",
		"%40", "%41", "%42", "%43", "%44", "%45", "%46", "%47",
		"%48", "%49", "%4a", "%4b", "%4c", "%4d", "%4e", "%4f",
		"%50", "%51", "%52", "%53", "%54", "%55", "%56", "%57",
		"%58", "%59", "%5a", "%5b", "%5c", "%5d", "%5e", "%5f",
		"%60", "%61", "%62", "%63", "%64", "%65", "%66", "%67",
		"%68", "%69", "%6a", "%6b", "%6c", "%6d", "%6e", "%6f",
		"%70", "%71", "%72", "%73", "%74", "%75", "%76", "%77",
		"%78", "%79", "%7a", "%7b", "%7c", "%7d", "%7e", "%7f",
		"%80", "%81", "%82", "%83", "%84", "%85", "%86", "%87",
		"%88", "%89", "%8a", "%8b", "%8c", "%8d", "%8e", "%8f",
		"%90", "%91", "%92", "%93", "%94", "%95", "%96", "%97",
		"%98", "%99", "%9a", "%9b", "%9c", "%9d", "%9e", "%9f",
		"%a0", "%a1", "%a2", "%a3", "%a4", "%a5", "%a6", "%a7",
		"%a8", "%a9", "%aa", "%ab", "%ac", "%ad", "%ae", "%af",
		"%b0", "%b1", "%b2", "%b3", "%b4", "%b5", "%b6", "%b7",
		"%b8", "%b9", "%ba", "%bb", "%bc", "%bd", "%be", "%bf",
		"%c0", "%c1", "%c2", "%c3", "%c4", "%c5", "%c6", "%c7",
		"%c8", "%c9", "%ca", "%cb", "%cc", "%cd", "%ce", "%cf",
		"%d0", "%d1", "%d2", "%d3", "%d4", "%d5", "%d6", "%d7",
		"%d8", "%d9", "%da", "%db", "%dc", "%dd", "%de", "%df",
		"%e0", "%e1", "%e2", "%e3", "%e4", "%e5", "%e6", "%e7",
		"%e8", "%e9", "%ea", "%eb", "%ec", "%ed", "%ee", "%ef",
		"%f0", "%f1", "%f2", "%f3", "%f4", "%f5", "%f6", "%f7",
		"%f8", "%f9", "%fa", "%fb", "%fc", "%fd", "%fe", "%ff"
	};

	/*******************************************************************************
	 * Properties
	 *******************************************************************************/

	private URLEncoderOptions encoderOptions;
	
	/*******************************************************************************
	 * Constructors
	 *******************************************************************************/
	
	public URLEncoder() {
		// Creating the encoder with default options
		this.encoderOptions = new URLEncoderOptions();
	}

	public URLEncoder(URLEncoderOptions pEncoderOptions) {
		// Creating the encoder with a specified set of options
		this.encoderOptions = pEncoderOptions;
	}
	
	/*******************************************************************************
	 * Public Methods
	 *******************************************************************************/

	/**
	 * Encode a string to the "x-www-form-urlencoded" form, enhanced
 	 * with the UTF-8-in-URL proposal. This is what happens:
	 *
	 * <ul>
	 * <li><p>The ASCII characters 'a' through 'z', 'A' through 'Z',
	 *        and '0' through '9' remain the same.
	 *
	 * <li><p>The unreserved characters - _ . ! ~ * ' ( ) remain the same.
	 *
	 * <li><p>The space character ' ' is converted into a plus sign '+'.
	 *
	 * <li><p>All other ASCII characters are converted into the
	 *        3-character string "%xy", where xy is
	 *        the two-digit hexadecimal representation of the character
	 *        code
	 *
	 * <li><p>All non-ASCII characters are encoded in two steps: first
	 *        to a sequence of 2 or 3 bytes, using the UTF-8 algorithm;
	 *        secondly each of these bytes is encoded as "%xx".
	 * </ul>
	 *
	 * @param s The string to be encoded
	 * @return The encoded string
	*/
	public String encode(String pSource) {
		StringBuffer encodingString = new StringBuffer();
		int sourceLength = pSource.length();
		for (int i = 0; i < sourceLength; i++) {
			int ch = pSource.charAt(i);
			if ('A' <= ch && ch <= 'Z') {		// 'A'..'Z'
				encodingString.append((char)ch);
			} else if ('a' <= ch && ch <= 'z') {	// 'a'..'z'
				encodingString.append((char)ch);
			} else if ('0' <= ch && ch <= '9') {	// '0'..'9'
				encodingString.append((char)ch);
			} else if ( !this.encoderOptions.isEncodeForwardSlashes() && ('/' == (char)ch)) {
				encodingString.append((char)ch);
			} else if (ch == ' ') {			// space
				encodingString.append('+');
			} else if (ch == '/') {			// space
				encodingString.append('+');
			} else if (ch == '-' || ch == '_'		// unreserved
				|| ch == '.' || ch == '!'
				|| ch == '~' || ch == '*'
				|| ch == '\'' || ch == '('
				|| ch == ')') {
				encodingString.append((char)ch);
			} else if (ch <= 0x007f) {		// other ASCII
				encodingString.append(hexCharacters[ch]);
			} else if (ch <= 0x07FF) {		// non-ASCII <= 0x7FF
				encodingString.append(hexCharacters[0xc0 | (ch >> 6)]);
				encodingString.append(hexCharacters[0x80 | (ch & 0x3F)]);
			} else {					// 0x7FF < ch <= 0xFFFF
				encodingString.append(hexCharacters[0xe0 | (ch >> 12)]);
				encodingString.append(hexCharacters[0x80 | ((ch >> 6) & 0x3F)]);
				encodingString.append(hexCharacters[0x80 | (ch & 0x3F)]);
			}
		}
		
		if (log.isDebugEnabled()) {
			log.debug("Source string: " + pSource + " was encoded to: " + encodingString.toString());
		}
		
		return encodingString.toString();
	}

	/*******************************************************************************
	 * Getters / Setters
	 *******************************************************************************/

	public URLEncoderOptions getEncoderOptions() {
		return this.encoderOptions;
	}
	
}
